Oliver - What did you tell me your threshold was?
Around 0.3 ppt. I am pretty sure that a lot of seasoned tasters are around 1-2 ppt, judging by the reaction of our customers to two batches of wine that were consistently 1.0 ppt.
They can detect TCA in a lab at .5 ppt reliably, apparently.
Oliver: When you and your associates are aware of TCA at these extremely low levels, is it because of the perception of the typical aroma profiles of TCA ( wet newspaper, mustiness, etc) or is it because how the fruit has been affected?
This possible mechanism seems likely to be an old wives tale that can’t be true. There must be another mechanism. The study cited by Mike Evans above is fascinating, but it’s a single cell neuroscience experiment that is pretty far removed from the complexity of human aroma/taste senses. I’ve tried to look for a study where a wine is dosed with successively increasing amounts of TCA, and a human panel is asked to evaluate the wines, but have never found that. Seems like a great project for a Davis grad student (or, frankly, undergrad, it’s so simple to do).
This topic continues to be amaze me for a number of reasons:
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It is common to sit in a room with winemakers or knowledgeable wine consumers and have some be convinced that a wine is affected by TCA and others not think it is.
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The vast majority of consumers have no clue as to what TCA is or how to pick it out - and we as an industry have gone backwards educating them.
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If a wine is affected by low levels of TCA, there is no doubt that it will strip a wine of its aromatics - the ‘challenge’ is that you will need another bottle that is unaffected to truly know that that’s the case.This remains the biggest challenge - without A/B comparisons, we truly are ‘guessing’ . . .
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Detection thresholds vary greatly - from .5ppt to over 10ppt, but from what I’ve always been lead to believe, most consumers can pick out a corked wine at 3-5ppt IF THEY KNOW WHAT THEY ARE LOOKING FOR.
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Also from what I understand, TCA never blows off - I read lots of notes the seem to say it does but my guess is in those situations, one’s senses become desensitized to TCA and therefore no longer detect it.
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You will most likely not see much research on this because who is going to pay for it? Not the cork companies or the Portugese government, who have supported other research studies. They really have nothing to gain by doing so . . .
Love the topic - keep it going folks . . .
I think that TCA has no effect on the taste of a wine if its concentration is below the threshold of an individual’s ability to perceive it. As Alan says, it is implausible that the molecule has a physical interaction with other molecules that affects the smell or taste of a contaminated (not “infected”) wine.
I also suspect that many people don’t really realize how vanishingly dilute a concentration of a few parts per trillion is. A trillion is a million million. When you test for chlorine is a swimming pool, you are looking at concentration on the level of parts per million. Parts per trillion is a million times less concentrated.
One part per trillion (ppt) denotes one part per 1,000,000,000,000 parts, one part in 1012, and a value of 1 × 10−12. This is equivalent to one drop of water (0.05 mL) diluted into 20 Olympic-size swimming pools (2,500 m3), or about three seconds out of every hundred thousand years.
I am talking about identifying the problem as TCA. These are professional wine buyers, of varying levels of experience.
Human sensitivity to TCA is truly amazing. Part of the TCA problem may be that it seems to be a recent development that the threshold for detection in a lab analysis has gotten close to human olfactory thresholds. It is easier to deny the problem if the lab can’t pick it up.
David,
I will respectfully disagree. If a wine is just slightly corked, perhaps below threshold for detecting the tell-tale wet cardboard or damp basement smell, it still ‘dumbs down’ the aromatics of the wine.
Have you ever been involved in cork trials? It’s fascinating how diverse the variation in corks can be from the same lot after sitting in wine overnight - simply amazing . . .
Cheers.
Sensing that a wine is “dumbed down” means that sensory receptors register the presence of the TCA molecule… the TCA concentration is thus above your threshold to detect it, whether you consciously recognize TCA or not…
Apparently there are two thresholds, the ‘difference threshold,’ which is where you can tell the sample is different from a clean sample, and the ‘identification threshold’ where you can tell the sample is different and detect the TCA note.
This is definitely not true. There’s a link upthread to a study that proves as much. I’ve also been in groups where there was a level detectable to some people but not others, and when a second (sound) bottle of the same wine was opened, every person at the table could notice the difference extremely clearly. I’ve never seen a single person say the two wines smelled identical to them, even those who have no problem drinking a mildly corked wine.
See Olivier’s post directly above yours.
Perception is not necessarily recognition.
It’s been my experience that TCA never blows off, but conversely is accentuated with air. If what you smell blows off, it was probably bottle stink.
Or actually gets accentuated when you place a few drops of water in the glass . . .
Cheers.
Ah, but here’s the wine world ‘fails us’ once again - how do you know if a wine is ‘dumbed down’ or ‘mildly corked’ or?!?!?!?
Unfortunately, we do not speak a common language in our industry, and the only way to ‘confirm’ what is going on with a wine is to take the wine (or cork) and have it analyzed . . . kind of like an autopsy, eh?
Cheers . . .
I tried to make it clear in the OP that my inquiries were regarding the perception of TCA, not its identification.That’s why I asked you that when you and your associates detect it at extremely low levels, what are the indicators or markers that tip you off. It could be the active smelling and/or tasting of certain aroma and/or flavor profiles. Or it could be the deduction that because there is little or no perception of fruit that the wine is tainted. I don’t think that you have to know what TCA is to be able to discern and say this wine smells like musty, wet cardboard that has been hanging around in a warm place.
Agree. Just assuming that a wine which doesn’t show well is affected by TCA below the otherwise sensory threshold has always seemed to me a bit dangerous. TCA might very well be the cause, but it could just as well be something else. Which is why I’d love to see a student do the progressive TCA addition test, using several different wines, with a group of people large enough to get some meaningful statistics. Such an easy, and useful project (and I still can’t believe it hasn’t been done, must just not have been published anywhere).
Michael, the post you quoted wasn’t aimed at you.
As you suggest, if someone knows it’s a musty cardboard smell it makes no difference whether or not they know what it’s called, it’s still identification. Almost no regular wine drinkers know what ‘corked’ or ‘tca’ mean, in my experience, which is what is so weird about this particular product defect.
For myself, there are times when a wine seems oddly subdued relative to other bottles or other vintages of the same wine, and I pay more attention to those bottles. It’s as if you’re listening to a familiar song but some of the notes are missing. Often TCA will emerge after a little while, sometimes it doesn’t. These days the examples of threshold taint for me have mostly been agglomerated corks, which are the bane of my existence, as the whole batch will be affected.
Having been involved in a lawsuit over 20,000 cases of cork tainted wine I think I have some interesting information:
- Cork industry consider tolerance at 2ppt…anything below that is “undetectable” by consumers
- Cork industry does not believe wine is affected by levels below 2ppt.
- I had 20,000 cases of Santa Maria Chardonnay with various levels of cork taint (technical agglomerated corks cleaned using steam)…some detectable to human nose, some not.
- I had a third party lab convene a panel of tasting experts to determine if the wines were being adversely affected even though cork supplier said they were not as they were below 2ppt in most instances. However, what the panel of tasters found was that there were varying impacts on the wine and tremendous bottle to bottle inconsistency. Basically, even at .5 and 1 ppt the wines were being adversely affected…something I call “insidious cork taint” - the consumer never knows the wines was tainted, just “blah”. This is also known as “fruit scalped” and I believe still a huge problem for wineries.
- Lawsuit went forward but cork supplier caved when they realized they were about to redefine the standards for cork taint.
- It also came to light that the corks that this supplier sold to me had been rejected by another winery for TCA levels (they’re big winery with lab)
- All 20,000 cases were crushed and then filtered off wine sold for $1/gallon.
- TCA impacts wines below the “(cork) industry standard” threshold.